1. Field of the Invention
The present invention relates to an internal combustion engine mounted on a vehicle or the like, and more specifically to an intake air amount control apparatus for the internal combustion engine for and an intake air amount control method thereof of performing fail-safe processing for the internal combustion engine which controls an intake air amount or an intake amount, by using an air-system variable mechanism provided with: a variable valve mechanism; an opening control mechanism of a throttle valve; and an intake characteristics change mechanism, such as a variable intake system (or xe2x80x9cAcoustic Control Induction System (ACIS))xe2x80x9d and a swirl control valve system (i.e. an intake airflow control mechanism), for example.
2. Description of the Related Art
In order to control the intake air amount or the intake amount, as for the internal combustion engine mounted on a vehicle or the a like, development has been recently proceeding with an internal combustion engine which employs a complicated air-system variable mechanism provided with: an electronic control or computerized throttle-valve mechanism for driving the opening and closing of a throttle valve by an actuator; a variable valve mechanism capable of varying at least one of three constituent elements of the opening/closing characteristics (or valve opening characteristics) of an intake valve or an exhaust valve (i.e. an opening and closing timing, an operating angle, and a lift amount); and an intake characteristics change mechanism, such as a variable intake system and a swirl control valve system (i.e. an intake airflow control mechanism), for example. Specifically, in order to obtain the desired or targeted torque corresponding to the accelerator opening operated by a driver, the control is performed so as to intake the desired or targeted intake air amount by cooperatively controlling the actuators of the various air-system variable mechanisms.
As an operating angle change mechanism, which is one of the above-described opening/closing characteristics, it is possible to exemplify a mechanism for continuously changing the operating angle of the intake valve and the lift amount by using a rotating cam, as described in Japanese Patent Application Laying Open NO. 2001-263015, for example.
Moreover, as described in Japanese Patent Application Laying Open NO. 2001-65376, for example, such a technique is also known that the opening and closing timing of the intake valve out of the constituent elements of the opening/closing characteristics is fixed to the most retarded or delayed time when an opening measurement sensor (e.g. a throttle position sensor) in the opening control mechanism of a throttle valve has a failure.
Moreover, as described in Japanese Patent Application Laying Open NO. Hei 10-184406, for example, such a technique is also known that the operating angle out of the opening/closing characteristics of the intake valve is fixed to the largest side in the internal combustion engine for controlling the intake air amount by adjusting the opening/closing characteristics of the intake valve and by the opening control mechanism of a throttle valve (e.g. an electronic control throttle valve), as the fail-safe processing upon the failure or malfunction of the opening control mechanism of a throttle valve.
Furthermore, as described in Japanese Patent Application Laying Open NO. 2001-65374, for example, such a technique is also known that the opening and closing timing of the intake valve is set to the most retarded or delayed time when a water thermometer has a failure.
However, if at least one of the above-described various air-system variable mechanisms has a failure, a situation may turn out to be what is usually not assumed as the control of the intake air amount in some cases. In this case, because the cooperative control among the opening control mechanism, the intake-air-characteristics change mechanism, and the variable valve mechanism diverges (i.e. the three mechanisms are no longer cooperatively controlled), the operating condition of the internal combustion engine possibly may become worse and an evacuation run may become impossible, which is technically a problem.
It is therefore an object of the present invention to provide an intake air amount control apparatus and an intake air amount control method for an internal combustion engine which can appropriately continue the operation thereof even in case that at least one of the three mechanisms has a failure or abnormality, for the internal combustion engine, in which the intake air amount is controlled by cooperatively controlling (i) the opening control mechanism of a throttle valve or the like, (ii) the intake characteristics change mechanism, such as the variable intake system and the swirl control valve system and (iii) the valuable valve mechanism, such as the operating angle change mechanism and a timing change mechanism (or Variable Valve Timing (VVT)).
The main purpose of the present invention is to prohibit the cooperative control to thereby prevent the divergence of the control and to preferably control the intake air amount of the internal combustion engine by one normal mechanism of (I) the opening control mechanism, (II) the variable valve mechanism and (III) the intake characteristics change mechanism, in case that there is an abnormality in any one of the three mechanisms in a technique of controlling the intake air amount of the internal combustion engine by the cooperative control of the three mechanisms.
The above object of the present invention can be achieved by a first intake air amount control apparatus for an internal combustion engine provided with: an opening control mechanism for controlling an opening of a throttle valve disposed on an intake path of the internal combustion engine; a variable valve mechanism for varying opening/closing characteristics (which mean both of the opening characteristic and the closing characteristics, or may mean one of the opening characteristic and the closing characteristic) of at least one of an intake valve and an exhaust valve of the internal combustion engine; an intake characteristics change mechanism for changing the intake characteristics of the internal combustion engine by controlling a parameter or parameters different from (i) the opening of the throttle valve and (ii) the opening/closing characteristics of the at least one of the intake valve and the exhaust valve; an intake amount control device for controlling an intake air amount supplied into a combustion chamber of the internal combustion engine by performing a cooperative control of the opening control mechanism, the variable valve mechanism and the intake characteristics change mechanism; an abnormality detection device for detecting an abnormal condition in the opening control mechanism and the variable valve mechanism; and a fail-safe device for controlling the opening control mechanism, the variable valve mechanism, and the intake characteristics change mechanism, in case that the abnormal condition is detected by the abnormality detection device in one of the opening control mechanism and the variable valve mechanism, so as to control the intake air amount by the other of the opening control mechanism and the variable valve mechanism, in place of the cooperative control by the intake amount control device.
According to the first intake air amount control apparatus for the internal combustion engine of the present invention, upon the operation thereof, the intake air amount supplied into the combustion chamber is controlled by that the three mechanisms, which are (I) the opening control mechanism of a throttle valve; (II) the variable valve mechanism; and (III) the intake characteristics change mechanism, are cooperatively controlled by the intake amount control device. More specifically, for example, while the intake air amount accompanying changes in the opening of the throttle valve according to the accelerator opening is measured by an intake amount measurement apparatus, the opening of the throttle valve is controlled by the opening control mechanism. At the same time of this, the opening/closing characteristics of at least one of the intake valve and the exhaust valve is controlled by the variable valve mechanism. The xe2x80x9copening/closing characteristicsxe2x80x9d associated with the present invention is the opening and closing timing of at least one of the intake valve and the exhaust valve, the lift amount, or a lift period (i.e. the operating angle). Moreover, at the same time of these, a predetermined parameter associated with the intake characteristics are controlled by the intake characteristics change mechanism, such as a swirl control valve, a variable intake system control valve, and the timing change mechanism, for example. The xe2x80x9cintake characteristicsxe2x80x9d associated with the present invention is: the adjustment amount of the opening of the swirl control valve as described later; the adjustment amount of the length of an effective intake tube, the capacity of a serge tank, the capacity and the cross sectional area of an intake port or an intake tube, or the like, which are the variable intake system control valve; and the adjustment amount of a phase angle for changing the opening and closing timing of the intake valve or the exhaust valve. For example, a desired or target intake air amount is determined by the intake amount control device according to the parameter for indicating the operating condition, such as a required (or desired) torque according to the number of engine revolutions and the accelerator opening operated by a driver (or an operator). In order to obtain this intended desired intake air amount, various control amounts associated with the opening/closing characteristics or the like which are desired are determined on the basis of a preset parameter table or a preset predetermined function, for example. The actuators of the three air-system variable mechanisms are cooperatively controlled by the intake amount control device so as to correspond to the desired various control amounts. Under such a cooperative control, the internal combustion engine is operated.
For example, when there is an abnormal condition in the opening control mechanism of the throttle valve, the abnormality is detected by the abnormality detection device. The abnormality which is detected specifically means, for example, the condition that the difference between the actual opening of the opening control mechanism of the throttle valve and the opening of the opening control mechanism of the throttle valve indicated by the intake amount control device is larger than a predetermined threshold value. Alternatively, when there is an abnormal condition in the variable valve mechanism, the abnormality is detected by the abnormality detection device. The abnormality which is detected specifically is, for example, an open-side failure (i.e. such a failure that the intake valve deviates to an open side to operate as compared with the normal case for some causes or that it is fixed to the open side) or an close-side failure (i.e. such a failure that the intake valve deviates to a close side to operate as compared with the normal case for some causes or that it is fixed to the close side).
When such an abnormality is detected by the abnormality detection device in one of (I) the opening control mechanism of the throttle valve and (II) the variable valve mechanism, the intake air amount is controlled by the other of the opening control mechanism and the variable valve mechanism, in which the abnormality is not detected, i.e. by the normal opening control mechanism or the normal variable valve mechanism, under the control of the fail-safe device, in place of the cooperative control by the intake amount control device for the above-described three mechanisms. In this manner, in the present invention, the three mechanisms are controlled under the control of the xe2x80x9cfail-safe devicexe2x80x9d upon the occurrence of any abnormal condition while the three mechanisms are controlled under the control of the xe2x80x9cintake amount control devicexe2x80x9d in the normal condition. The xe2x80x9cfail-safe devicexe2x80x9d and the xe2x80x9cintake amount control devicexe2x80x9d may comprise the same controller (e.g. an ECU described later) or the same control device which can perform both of the control upon the occurrence of any abnormal condition and the control in the normal condition. Alternatively, they may comprise different exclusive controllers or different control devices which can separately perform the control upon the occurrence of any abnormal condition and the control in normal condition.
As a result, for example, the fuel injection is performed in each cylinder according to the intake air amount controlled by the normal variable valve mechanism and the number of engine revolutions. Alternatively, for example, the fuel injection is performed in each cylinder according to the intake air amount controlled by the normal opening control mechanisms of the throttle valve and the number of engine revolutions.
One specific example of the intake characteristics change mechanism of the present invention, that is, the xe2x80x9cvariable intake system (or ACIS)xe2x80x9d is a mechanism whose purpose is to obtain the high volume efficiency in the broad range of engine revolutions by varying the length and the cross sectional area of the effective intake tube. Specifically, in a low-speed operation, the variable intake system makes the length of the effective intake tube relatively long and the cross section area thereof relatively small in order to increase the volume efficiency at low revolutions, by using a resonance supercharged effect. On the other hand, in a high-speed operation, the variable intake system is realized by making the length of the effective intake tube relatively short and the cross section area thereof relatively large in order to increase the volume efficiency at high revolutions, by using the inertia supercharged effect. Moreover, a mechanisms of varying the capacity of a serge tank is also conceivable as a specific example as it carries the same function.
Another specific example of the intake characteristics change mechanism of the present invention, that is, the xe2x80x9cSwirl Control Valve System (SCV)xe2x80x9d is a mechanism which makes the intake port function as a swirl port which generates a lateral excess flow to mix fuel and the air sufficiently or which uses the intake port as a typical port by varying the direction of a valve disposed in the intake port, thereby to realize both the increase of the output and the improvement of the fuel consumption. Moreover, a xe2x80x9cTumble Control Valve System (TCV)xe2x80x9d which functions as a tumble port for generating a longitudinal excess flow is also conceivable as a specific example as it carries the same function.
Moreover, another specific example of the intake characteristics change mechanism of the present invention, that is, the xe2x80x9ctiming change mechanism (or VVT)xe2x80x9d of the intake valve and/or the exhaust valve is a mechanism which changes the opening and closing timing of the intake valve and the exhaust valve thereby to realize the efficient intake and/or the exhaust according to the number of engine revolutions and the desired torque, and by which the intake air amount can be controlled. In the present invention, such a timing change mechanism (or VVT) can be treated as the specific example of the xe2x80x9cintake characteristics change mechanismxe2x80x9d. It can also be treated as a part or all of the xe2x80x9cvariable valve mechanismxe2x80x9d for varying the operating angles of the intake valve and the exhaust valve or the lift amount associated with the present invention.
Consequently, even if one of the opening control mechanism of the throttle valve and the variable valve mechanism, which constitute the air-system variable mechanism, has a failure, the intake air amount is controlled by the other of the opening control mechanism and the variable valve mechanism, in which the abnormality is not detected, i.e. by the normal opening control mechanism or the normal variable valve mechanism, under the control of the fail-safe device. Namely, the evacuation run sufficiently becomes possible by performing the simple intake-air-amount control by the mechanism in which there is not any abnormality. In other words, the evacuation run sufficiently becomes possible even upon the occurrence of an abnormal condition, while the present invention adopts such a structure that the internal combustion engine is operated under the cooperative control of actuators in various air-system variable mechanisms, which is suitable for the high fuel consumption and/or the high efficiency in the normal condition, so that the present invention is extremely useful in practice.
In particular, when there is an abnormality in one of the three mechanisms, the control for the evacuation run is performed not by the other two normal mechanisms but by the other one normal mechanism (i.e., by the just one normal mechanism). Therefore, the control for the evacuation run is relatively simple. If the control is performed by the other two normal mechanisms, it is necessary to perform a cooperative control for the two and it is necessary to have some parameter table and/or some exclusive function for specifying various control amounts only for the evacuation run. For example, if the variable intake system control valve causes the open-side-failure, the actual intake air amount increases and the number of engine revolutions increases. If the number of engine revolutions increases, a desired intake air amount is usually set to be small, but this is not an assumed condition, so one of the two normal mechanisms, that is, the opening control mechanism of the throttle valve may be driven too much to the close side, or another normal mechanism, that is, the variable valve mechanism may be driven too much to the close side, thereby possibly causing hunching (i.e. periodic vibration generated upon the idle rotation of the engine). Thus, it is necessary to prepare many parameter tables and exclusive functions corresponding to various aspects of the abnormality for the xe2x80x9cevacuation runxe2x80x9d in which an efficient run is extremely difficult or impossible due to the abnormality, and as a whole, it becomes extremely wasteful. On the contrary, realizing the control of the intake air amount by one mechanism, which is, for example, the opening control mechanism of the throttle valve or the variable valve mechanism, is far simple and easy, so that it can be certainly performed.
As described above, according to the first intake air amount control apparatus for the internal combustion engine of the present invention, the evacuation run can be performed more certainly in the internal combustion engine provided with a plurality of air-system variable mechanisms, such as the opening control mechanism of a throttle valve, the variable valve mechanism, and the intake characteristics change mechanism, for example.
In one aspect of the first intake air amount control apparatus of the present invention, the fail-safe device fixes (i) a control amount by the one of the opening control mechanism and the variable valve mechanism and (ii) a control amount by the intake characteristics change mechanism to be constant values in spite of an operation condition of the internal combustion engine, in case that the abnormal condition is detected in the one of the opening control mechanism and the variable valve mechanism.
According to this aspect, when the abnormality is detected in the one of the opening control mechanism of the throttle valve and the variable valve mechanism, not only the control amount by the one mechanism in which the abnormality is detected but also the control amount by the intake characteristics change mechanism, such as the above-described swirl control valve and the variable intake system control valve, are fixed to the constant values in spite of the operation condition. The xe2x80x9ccontrol amountsxe2x80x9d associated with the present invention indicate the adjustment amount of the opening of the throttle valve in the opening control mechanism of the throttle valve, the adjustment amount of the opening/closing characteristics of the intake valve in the variable valve mechanism, and the adjustment amount of the predetermined parameter or parameters in the intake characteristics change mechanism. Then, the intake air amount is controlled by the other of the opening control mechanism and the variable valve mechanism, in which the abnormality is not detected, i.e. by the normal opening control mechanism or the normal variable valve mechanism, under the control of the fail-safe device, while the control amounts are fixed to constant values as described above. As a result, for example, the fuel injection is controlled in each cylinder according to the intake air amount controlled by the normal variable valve mechanism and the number of engine revolutions. Alternatively, for example, the fuel injection is controlled in each cylinder according to the intake air amount controlled by the normal opening control mechanisms of the throttle valve and the number of engine revolutions.
Consequently, even if the opening control mechanism of the throttle valve or the variable valve mechanism, which constitute the air-system variable mechanism, has a failure, the evacuation run sufficiently becomes possible by fixing various control amounts not only in the mechanism in which there is the abnormality but also in the intake characteristics change mechanism and by performing the simple intake-air-amount control by the mechanism in which there is not any abnormality.
Incidentally, in place of fixing both of the control amount by the mechanism in which the abnormality is detected and the control amount by the intake characteristics change mechanism to the constant values as described above, the present invention can be constructed such that the control for the two mechanisms is stopped or that the control amounts are fixed to some constant values (e.g. unknown values or default values) by stopping the control for the two mechanisms. Moreover, it may be constructed such that the control amounts change regularly or irregularly around some predetermined values or in a predetermined range (e.g. around unknown values or default values) by stopping the control. By constituting in this manner, it is possible to obtain a reasonable effect by shifting to the simple control for the one mechanism upon the occurrence of an abnormal condition, although this is inferior to the above-described aspect. The structure with such a xe2x80x9ccontrol stopxe2x80x9d as described above is also included in the technical scope associated with the first intake air amount control apparatus of the present invention.
The above object of the present invention can be achieved by a second intake air amount control apparatus for an internal combustion engine provided with: an opening control mechanism for controlling an opening of a throttle valve disposed on an intake path of the internal combustion engine; a variable valve mechanism for varying opening/closing characteristics of at least one of an intake valve and an exhaust valve of the internal combustion engine; an intake characteristics change mechanism for changing intake characteristics of the internal combustion engine by controlling a parameter or parameters different from (i) the opening of the throttle valve and (ii) the opening/closing characteristics of the at least one of the intake valve and the exhaust valve; an intake amount control device for controlling an intake air amount supplied into a combustion chamber of the internal combustion engine by performing a cooperative control of the opening control mechanism, the variable valve mechanism and the intake characteristics change mechanism; an abnormality detection device for detecting an abnormal condition in the intake characteristics change mechanism; and a fail-safe device for controlling the opening control mechanism, the variable valve mechanism and the intake characteristics change mechanism in case that the abnormal condition is detected by the abnormality detection device in the intake characteristics change mechanism, so as to control the intake air amount by one of the opening control mechanism and the variable valve mechanism, in place of the cooperative control by the intake amount control device.
According to the second intake air amount control apparatus of the present invention, upon the operation thereof, the intake air amount supplied into the combustion chamber is controlled by that the cooperative control is controlled by the intake amount control device, as in the case of the first intake air amount control apparatus of the present invention described above.
In the case of the second intake air amount control apparatus of the present invention, for example, when there is any abnormal condition in the intake characteristics change mechanism, the abnormality is detected by the abnormality detection device. The abnormality which is detected specifically means, for example, the condition that the difference between (i) the actual experimental value (including both a directly or indirectly measured value and an estimated value) of the predetermined parameter associated with the intake characteristics change mechanism and (ii) the predetermined parameter of the intake characteristics change mechanism indicated by the intake amount control device is larger than a predetermined threshold value.
When such an abnormality is detected by the abnormality detection device in the intake characteristics change mechanism, the intake air amount is controlled by one of the opening control mechanism and the variable valve mechanism under the control of the fail-safe device, in place of the cooperative control by the intake amount control device for the above-described three mechanisms. As a result, for example, the fuel injection is controlled in each cylinder according to the intake air amount controlled by the normal opening control mechanisms of the throttle valve and the number of engine revolutions. Alternatively, for example, the fuel injection is controlled in each cylinder according to the intake air amount controlled by the normal variable valve mechanism and the number of engine revolutions.
Consequently, the evacuation run sufficiently becomes possible even upon the occurrence of an abnormal condition, while the present invention adopts such a structure that the internal combustion engine is operated under the cooperative control of actuators in various air-system variable mechanisms, which is suitable for the high fuel consumption and/or the high efficiency in the normal condition.
In one aspect of the second intake air amount control apparatus of the present invention, the fail-safe device fixes (i) a control amount by the intake characteristics change mechanism and (ii) a control amount by the other of the opening control mechanism and the variable valve mechanism to constant values in spite of an operation condition of the internal combustion engine, in case that the abnormal condition is detected in the intake characteristics change mechanism.
According to this aspect, when the abnormality is detected in the intake characteristics change mechanism, not only the control amount by the intake characteristics change mechanism in which the abnormality is detected but also the control amount by the other of the opening control mechanism and the variable valve mechanism as described above are fixed to be constant values in spite of the operation condition. Then, the intake air amount is controlled by the one of the opening control mechanism and the variable valve mechanism as described above under the control of the fail-safe device, while the control amounts are fixed to constant values as described above.
As a result, for example, the fuel injection is controlled in each cylinder according to the intake air amount controlled by the normal opening control mechanisms of the throttle valve and the number of engine revolutions. Alternatively, for example, the fuel injection is controlled in each cylinder according to the intake air amount controlled by the normal variable valve mechanism and the number of engine revolutions. As described above, even if the intake characteristics change mechanism has a failure, the evacuation run sufficiently becomes possible by shifting to the simple intake-air-amount control.
Incidentally, in place of fixing the control amounts to the constant values as described above, the present invention can be constructed such that the control is stopped or that the control amounts are fixed to some constant values by stopping the control. Moreover, it may be constructed such that the control amounts change regularly or irregularly around some predetermined values or in a predetermined range by stopping the control.
The above object of the present invention can be achieved by a third intake air amount control apparatus for an internal combustion engine provided with: an opening control mechanism for controlling an opening of a throttle valve disposed on an intake path of the internal combustion engine; a variable valve mechanism for varying the opening/closing characteristics of at least one of an intake valve and an exhaust valve of the internal combustion engine; an intake characteristics change mechanism for changing intake characteristics of the internal combustion engine by controlling a parameter or parameters different from (i) the opening of the throttle valve and (ii) the opening/closing characteristics of the at least one of the intake valve and the exhaust valve; an intake amount control device for controlling an intake air amount supplied into a combustion chamber of the internal combustion engine by performing a cooperative control of the opening control mechanism, the variable valve mechanism and the intake characteristics change mechanism; an abnormality detection device for detecting an abnormal condition in the opening control mechanism, the variable valve mechanism, and the intake characteristics change mechanism; and a fail-safe device for controlling the opening control mechanism, the variable valve mechanism, and the intake characteristics change mechanism, in case that the abnormal condition is detected by the abnormality detection device in one of the opening control mechanism, the variable valve mechanism, and the intake characteristics change mechanism, so as to control the intake air amount by another of the opening control mechanism, the variable valve mechanism, and the intake characteristics change mechanism, in place of the cooperative control by the intake amount control device.
According to the third intake air amount control apparatus of the present invention, upon the operation thereof, the intake air amount supplied into the combustion chamber is controlled by that the cooperative control is controlled by the intake amount control device, as in the case of the first intake air amount control apparatus of the present invention described above.
In the case of the third intake air amount control apparatus of the present invention, for example, when there is any abnormal condition in the opening change mechanism of the throttle valve, the abnormality is detected by the abnormality detection device. Alternatively, for example, when there is any abnormal condition in the variable valve mechanism, the abnormality is detected by the abnormality detection device. Moreover, for example, when there is any abnormal condition in the intake characteristics change mechanism, the abnormality is detected by the abnormality detection device.
When such an abnormality is detected by the abnormality detection device in one of the three mechanisms, the intake air amount is controlled by another of the opening control mechanism, the variable valve mechanism, and the intake characteristics change mechanism, in which the abnormality is not detected, i.e. by another of the normal opening control mechanism, variable valve mechanism, and intake characteristics change mechanism, in place of the cooperative control by the intake amount control device for the above-described three mechanisms. As a result, for example, the fuel injection is controlled in each cylinder according to the intake air amount controlled by the normal variable valve mechanism and the number of engine revolutions. Alternatively, for example, the fuel injection is controlled in each cylinder according to the intake air amount controlled by the normal opening control mechanisms of the throttle valve and the number of engine revolutions. Moreover, for example, the fuel injection is controlled in each cylinder according to the intake air amount controlled by the intake characteristics change mechanism and the number of engine revolutions.
Consequently, the evacuation run sufficiently becomes possible even upon the occurrence of an abnormal condition, while the present invention adopts a structure suitable for the high fuel consumption and/or the high efficiency in the normal condition.
In one aspect of the third intake air amount control apparatus of the present invention, the fail-safe device fixes (i) a control amount by the one of the opening control mechanism, the variable valve mechanism, and the intake characteristics change mechanism and (ii) a control amount by another of the three mechanisms, to constant values in spite of an operation condition of the internal combustion engine, in case that the abnormal condition is detected in the one of the three mechanisms.
According to this aspect, when the abnormality is detected in one of the three mechanisms (i.e., the opening control mechanism, the variable valve mechanism and the intake characteristics change mechanism), not only the control amount by the mechanism in which the abnormality is detected but also the control amount by the another of the three mechanisms in which the abnormality is not detected is fixed to the constant value in spite of the operation condition. Then, the intake air amount is controlled by the rest of the three mechanisms in which the abnormality is not detected, under the control of the fail-safe device, while the control amounts for the two mechanisms are fixed to the constant values as described above.
As a result, for example, the fuel injection is controlled in each cylinder according to the intake air amount controlled by the normal variable valve mechanism and the number of engine revolutions. Alternatively, for example, the fuel injection is controlled in each cylinder according to the intake air amount controlled by the normal opening control mechanisms of the throttle valve and the number of engine revolutions. Moreover, for example, the fuel injection is controlled in each cylinder according to the intake air amount controlled by the intake characteristics change mechanism and the number of engine revolutions. As described above, even if any one of the three mechanisms has a failure, the evacuation run sufficiently becomes possible by shifting to the simple intake-air-amount control.
Incidentally, in place of fixing the control amounts to the constant values as described above, the present invention can be constructed such that the control is stopped or that the control amounts are fixed to some constant values by stopping the control. Moreover, it may be constructed such that the control amounts change regularly or irregularly around some predetermined values or in a predetermined range by stopping the control.
In another aspect of the second intake air amount control apparatus of the present invention, the fail-safe device controls the opening control mechanism, the variable valve mechanism and the intake characteristics change mechanism, in case that the abnormal condition is detected in the intake characteristics change mechanism, so as to control the intake air amount by the opening control mechanism.
According to this aspect, when the abnormality is detected in the intake characteristics change mechanism, the intake air amount is controlled by the opening control mechanism under the control of the fail-safe device. As a result, the fuel injection is controlled in each cylinder according to the intake air amount controlled by the normal opening control mechanisms of the throttle valve and the number of engine revolutions.
In another aspect of the third intake air amount control apparatus of the present invention, the fail-safe device controls the opening control mechanism, the variable valve mechanism and the intake characteristics change mechanism, in case that the abnormal condition is detected in the variable valve mechanism or the intake characteristics change mechanism as the one of the three mechanisms, so as to control the intake air amount by the opening control mechanism as the another of the three mechanisms.
According to this aspect, when the abnormality is detected in the variable valve mechanism or the intake characteristics change mechanism, the intake air amount is controlled by the opening control mechanism of the throttle valve in which the abnormality is not detected, i.e. by the normal opening control mechanism, under the control of the fail-safe device. As a result, the fuel injection is controlled in each cylinder according to the intake air amount controlled by the normal opening control mechanisms of the throttle valve and the number of engine revolutions.
In another aspect of the first, second, or third intake air amount control apparatus of the present invention, the constant values are values which relatively reduce concentration of predetermined impurity or impurities in an exhaust gas generated by the internal combustion engine.
According to this aspect, the operating angle, which is the control amount of the variable valve mechanism, such as the operating angle change mechanism, is arbitrarily fixed. The swirl control valve and the variable intake system control valve are fixed to the close side. The opening timing of the intake valve is set to be the most retarded or delayed, and the closing timing of the exhaust valve is set to be the most advanced or the earliest. As a result, by minimizing or substantially minimizing a time length in which the intake valve and the exhaust valve are both open, i.e. a xe2x80x9cvalve overlap amountxe2x80x9d, it is possible to prevent a combustion exhaust gas from returning to the intake valve, which makes it possible to relatively reduce the concentration of predetermined impurity or impurities in the exhaust gas generated in the internal combustion engine. As described above, when two of the control amounts of the three mechanisms are fixed to constant values, the two of the control amounts are fixed to the constant values so as to reduce the concentration of predetermined impurities, such as NOx, in an exhaust gas, which can prevent the reduction of exhaust gas characteristics in the evacuation run to a greater or lesser extent.
In another aspect of the first, second, or third intake air amount control apparatus of the present invention, the constant values are values corresponding to the operating condition in a partial load area of the internal combustion engine.
According to this aspect, the operating angle, such as the operating angle change mechanism, is arbitrarily fixed. The swirl control valve and the variable intake system control valve are fixed to the close side. The opening timing of the intake valve is set to be the most retarded or delayed, and the closing timing of the exhaust valve is set to be the most advanced or the earliest. There is hardly any necessity to operate the engine at the high-speed rotations and on the high load in the xe2x80x9cevacuation runxe2x80x9d upon the occurrence of an abnormal condition. Thus, it is useful to reduce a possibility of an accidental fire and perform the evacuation run by operating the engine at the low number of engine revolutions and on the low load as in this aspect, in performing the evacuation run safely and certainly or preventing the reduction of the exhaust gas characteristics.
In another aspect of the first, second, or third intake air amount control apparatus of the present invention, the intake characteristics change mechanism includes at least one of (i) a swirl control valve for controlling the intake air amount by adjusting swirl in the combustion chamber, (ii) a variable intake system control valve for controlling the intake air amount by adjusting the intake path leading to the combustion chamber and (iii) a timing change mechanism for controlling the intake air amount by adjusting opening/closing timing (i.e., opening timing and/or closing timing) of at least one of the intake valve and the exhaust valve.
According to this aspect, upon the normal operation, the intake air amount is controlled by that the predetermined parameter is adjusted by the intake characteristics change mechanism, such as the swirl control valve, the variable intake system control valve, and the timing change mechanism, through the cooperation with the opening control mechanism of a throttle valve and the variable valve mechanism. Particularly, as the variable intake system control valve, there are a valve for varying the length of the effect intake tube, a valve for varying the capacity of the serge tank, a valve for varying the capacity or the cross sectional area of the intake port or the intake tube, or the like. When the abnormality is detected in such an intake characteristics change mechanism, the control amount of the intake characteristics change mechanism is fixed to a constant value. Alternatively, when the abnormality is detected in the variable valve mechanism or the opening control mechanism, the control amount of the intake characteristics change mechanism is fixed to a constant value.
The above object of the present invention can be achieved by an intake air amount control method for an internal combustion engine of controlling an intake air amount of the internal combustion engine by performing a cooperative control of (I) an opening control mechanism for controlling an opening of a throttle valve disposed on an intake path of the internal combustion engine, (II) a variable valve mechanism for varying the opening/closing characteristics of at least one of an intake valve and an exhaust valve of the internal combustion engine and (III) an intake characteristics change mechanism for changing intake characteristics of the internal combustion engine by controlling a parameter or parameters different from (i) the opening of the throttle valve and (ii) the opening/closing characteristics of at least one of the intake valve and the exhaust valve, wherein the method controls the intake air amount, in case that there is any abnormality in one of the opening control mechanism, the variable valve mechanism, and the intake characteristics change mechanism, only by another of the opening control mechanism, the variable valve mechanism, and the intake characteristics change mechanism.
According to the intake air amount control method of the present invention, the evacuation run sufficiently becomes possible even upon the occurrence of an abnormal condition, while the present invention adopts the intake air amount control method by the cooperative control in the normal condition, as in the case of the above-described first, second or third intake air amount control apparatus of the present invention.
The nature, utility, and further features of this invention will be more clearly apparent from the following detailed description with reference to preferred embodiments of the invention when read in conjunction with the accompanying drawings briefly described below.